Adaptive selection of image streaming mode

ABSTRACT

A Picture Archiving and Communications System (PACS) transmits medical image information from a server to a viewing workstation. The mode of transmission that the system uses depends on a performance metric of the network. If the network is fast and stable, the entire DICOM image file is transmitted. If the network is not fast and stable, one of several other modes is used to transmit the image information.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the storage, archiving, networking,and retrieval of medical images and video, and more particularly toimprovements in a Picture Archiving and Communications System (PACS)operating in networks having different possible bandwidths.

2. Description of the Related Arts

A PACS is a system for the storage, retrieval, and display of medicalimages. A PACS typically consists of one or more networked computersalong with a substantial amount of semi-permanent digital storage in theform of, for instance, a RAID (redundant array of inexpensive harddisks), tape storage, or optical disks. A PACS also typically includessoftware for storing, retrieving, and displaying images, along withhardware that may be necessary for physical management of digital media(e.g., a robotic tape loader), display, and input.

A PACS is typically connected to an imaging device such as a CT(computerized tomography) scanner, an MRI (magnetic resonance imaging)scanner, or an X-ray machine capable of providing images in digitalformat, often including images compliant with the DICOM (Digital Imagingand Communications in Medicine) format. A doctor or other health careprovider uses the imaging device to create a digital picture of apatient for diagnosis or treatment purposes. The image is delivered viaa network to the PACS, where it is stored along with informationidentifying the particular patient. The image is viewed on the PACSimmediately or it is retrieved for display later. The image isoptionally processed prior to storage, or it is stored in a raw digitalformat and subjected to optional processing later.

Prior to the development of PACS technology, hospitals typically storedmedical images on film that had to be catalogued and retrieved by hand.Early computerized medical imaging devices were flawed because themachines were typically standalone devices with no or limited archivalcapabilities and proprietary file formats. PACS, along with the standardDICOM and other file formats, provided a convenient, standardized way tostore medical images with fast, electronic retrieval, more convenientbackup, and potential for remote electronic distribution.

Despite their advantages, traditional PACSs have numerous shortcomings.First, a traditional PACS may operate in connection with variousdifferent networks, each of which has a different bandwidth, or evenwith a single network having an effective bandwidth that varies withoverhead requirements, competing data traffic from other systems usingthe same network, and the like.

Known PACSs are configured to stream images using any of a number ofdata transfer protocols. Some protocols are particularly well adaptedfor high bandwidth networks, while others typically are optimized towork with lower bandwidth networks. Commonly, optimizing a protocol fora particular network bandwidth calls for certain design tradeoffs. Forexample, high bandwidth channels permit the transfer of image data withvery little preprocessing or post processing, thus imposing very littleoverhead on the devices used to store, retrieve, package, transmit,receive, and decode the data. Other communication channels, for examplewireless channels, may have a very wide bandwidth but suffer fromperiodic network failures, for example when a device's wirelesscommunications path is blocked by other equipment or where the devicegets out of range of the node it is communicating with. Still otherchannels, such as networks relying on conventional modem communicationsover telephone networks, particularly older POTS (“Plain old telephoneservice”) networks, have far less bandwidth. To achieve satisfactoryimage streaming using such low-bandwidth networks, significant datacompression/decompression must be used, typically calling forsignificant processing resources.

In many instances, it may be acceptable to choose a likely networkbandwidth for a PACS implementation, and select communication protocolsthat are optimized to work with such expected network. However,experience has shown that quite often such systems will end up operatingunder various network bandwidths, and it would be advantageous to have aPACS that could operate effectively in connection with a variety ofnetwork bandwidths.

Considering the situation in greater detail, medical images sharedacross one or more healthcare organizations are commonly stored in theDICOM format, which supports a variety of data representations,including raw pixel data, baseline lossless compression (lossless JPEG),and the progressive compression standard known as JPEG 2000. Healthcareorganization network infrastructures often suffer from bottlenecks,insufficiencies, instabilities and other problems that make imagestreaming using a preferred format impossible, for example because theimages cannot be fetched and rendered at a user's viewing workstationfast enough to appear in real time.

Simple known solutions, such as increasing network bandwidth, are notalways feasible, due to a variety of factors ranging from cost tohospital wiring policies.

Another possibility is conventional compression of the image data to bestreamed. In many medical applications, however, some types ofcompression, particularly lossy compression, are either disfavored oroutright forbidden. The concern is that medical diagnostic work is tooimportant and subtle a task to be burdened with additional uncertaintiesthat may arise by intentionally degrading an image from its originalnumber of pixels, bit depth, and other characteristics. Losslesscompression techniques, even when they are allowed, typically onlyreduce image file sizes by less than an order of magnitude, which inmany cases is not sufficient to provide real time streaming over lowbandwidth channels. Medical images are particularly ill-suited tolossless compression because many medical imaging modalities such as CTor ultrasound inherently produce images having significant pure noisecomponents that do not lend themselves to significant compression usingknown lossless methods.

Even where compression is workable, difficulties remain to be addressed.For example, the wavelet-based JPEG2000 image compression standardprovides progressive compression capabilities that allow thetransmission of images in separate “layers” of quality. An initiallytransmitted image improves with quality as more data arrive. In“lossless” mode, JPEG2000 processing allows transmission of the datauntil the received image is of the same quality as the original image.In some circumstances, use of this format provides some manner ofinherent adaptability to varying bandwidths, as once bandwidth dropsbelow the size needed for real time lossless transmission, transmissionsimply continues at somewhat lower quality, with images being discardedbefore they reach original-image quality.

A further known improvement using JPEG2000 is to transmit high qualityimages for only a particular region of interest (ROI) whenfull-bandwidth original-quality transmission is not possible.

These solutions may be available where original images are available ina DICOM format compliant with JPEG2000, but many imaging modalities donot make images available in such format. Even where such images areavailable, lossless JPEG2000 coding is computationally demanding,typically 5-6 times slower than comparable lossless coding under theprevious JPEG standard. Correspondingly, decoding and rendering of suchJPEG2000 images is likewise more computationally intensive, and mayresult in unacceptable performance on conventional viewing workstations.

U.S. Pat. No. 6,314,452 discloses one partial solution to thedifficulties in using JPEG2000 using wavelet streaming. However, thisand others of the known techniques still impose unnecessary overhead,for instance by still coding/decoding images when wide networkbandwidths are available and image transfer could be accomplishedwithout this additional processing.

Some on-demand video applications also address similar issues throughscalable video streaming and quality of service. Using the advancedcapabilities of the MPEG video compression standard, one can control therate/distortion tradeoff on a per-device (i.e., viewing device) basis.Accordingly, one can dynamically allocate a bitstream among variousviewing nodes and stream higher resolution video to higher resolutionviewing devices and higher visual quality to certain users. However,these solutions typically assume that video is streamed from a singlepre-processed MPEG file composed of resolution and quality layers—anassumption that is often not true in many medical applications.

In medical tele-radiology applications, the traditional solution hasbeen to schedule transfers of large lossless DICOM images in advance,during off-peak hours, so that a radiologist or other provider canreceive, store, and later review the images. Various techniques are usedto try to predict when off-peak slots will be available and match thatwith the healthcare needs associated with the images to be transmitted.

U.S. Pat. No. 6,848,004 discloses a system for adaptive delivery ofrich-media content in web pages. This document discloses a client-serversystem in which the client calculates the bandwidth and the serveradaptively transmits web content, with richer content being transmittedwhen higher bandwidth is available. This technique relies on theavailability of dynamically loading applet technologies, such as JAVAapplets, that may not be available in all situations.

Likewise, U.S. Pat. No. 6,243,761 discloses a method for dynamicallyadjusting multimedia content of a web page by a server according toeffective bandwidth and/or latency characteristics. In this instance,the content sent to the client computer is adjusted, such as by reducingthe size, resolution, or number of images of the graphic image. Whilesuch modification of content might be acceptable in many web-browserapplications, it may not be appropriate for many medical applications.

Another approach is described in Chandra, S. et al., Application-leveldifferentiated multimedia Web services using quality aware transcoding,18 IEEE Journal on Communications 12, December 2000, pp. 2544-2565, ISSN0733-8716 (“Chandra”). Chandra discloses use of application-specificcharacteristics of Web services to manage resources. Again, theenvironments of typical PACSs may not make such services available.Still other disclosures addressing some of these issues are Gaddah etal., Image transcoding proxy for mobile Internet access, Proceedings ofthe Vehicular Technology Conference 2002, September 2002, pp. 807-811,ISSN 1090-3038; Lee et al., SIQuA: server-aware image quality adaptationfor optimizing server latency and capacity in wireless image dataservices [mobile radio], Vehicular Technology Conference, 2004, 4VTC2004-Fall (IEEE), pp. 2611-2615, ISSN: 1090-3038; Kim et al, A newresource allocation scheme based on a PSNR criterion for wireless videotransmission to stationary receivers over Gaussian channels, IEEETransactions on Wireless Communications 1:3, July 2002, pp. 393-401,ISSN: 1536-1276; Raman et al. ITP: an image transport protocol for theInternet, IEEE/ACM Transactions on Networking 10:3, June 2002, pp.297-307, ISSN 1063-6692; U.S. Pat. Nos. 5,931,904 and 5,276,898.

Generalizing from the above, there remains a need for a system that usesadvanced processing to stream medical image data at acceptable qualitywhen available bandwidth is low, and that avoids doing such processingwhen it is not needed, for example when available bandwidth is high.

SUMMARY OF THE INVENTION

To address the above problems with traditional picture archiving andcommunications systems, in accordance with the present invention when auser requests an image, a viewer subsystem first determines theavailable bandwidth or, in some embodiments, other related parameterssuch as computational resources for pre-/post-processing of images, datatype and size, for streaming the image. In the event that high bandwidthis detected relative to the size of the image data, a streaming mode isselected that uses the image in its native (e.g., DICOM) form. In theevent that less bandwidth is available, one of several modes is selectedfor transmission, each requiring less bandwidth but more processingoverhead.

In one embodiment, a sequence of lower bandwidth modes includes losslesscompression, ROI streaming of pixel data, lossless compression of ROIpixel data, baseline wavelet lossless compression, and progressivewavelet lossless compression.

The features and advantages described in the specification are notall-inclusive and, in particular, many additional features andadvantages will be apparent to one of ordinary skill in the art in viewof the drawings, specification, and claims. Moreover, it should be notedthat the language used in the specification has been principallyselected for readability and instructional purposes, and may not havebeen selected to delineate or circumscribe the inventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention has other advantages and features which will be morereadily apparent from the following detailed description of certainembodiments of the invention and the appended claims, when taken inconjunction with the accompanying drawings, in which:

FIG. 1 illustrates in overview fashion interaction among basiccomponents of a system in accordance with the present invention.

FIG. 2 illustrates a flow diagram for image streaming processing inaccordance with the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The Figures and the following description relate to embodiments of thepresent invention by way of illustration only. It should be noted thatfrom the following discussion, alternative embodiments of the structuresand methods disclosed herein will be readily recognized as viablealternatives that may be employed without departing from the principlesof the claimed invention.

The present invention includes a system and method for transferringmedical images in a PACS. In embodiments detailed herein, streamingmodes are selected to adapt to given network bandwidth and stability.Where bandwidths are high and stable, simple file transfer of theoriginal image file is used. Where bandwidths are low or the networksunstable, slower and more forgiving modes of transfer are employed.

Referring now to FIG. 1, a system 100 in accordance with the presentinvention is shown by way of its basic components: a viewing workstation101, a network 110 and a server 120. System 100 is configured, as shown,to permit a user at viewing workstation 101 to request a medical imagefrom server 120, the image to be transmitted via network 110. In atypical embodiment, viewing workstation 101 is implemented by aconventional personal computer with appropriate display and networkconnection, configured as described herein. Likewise, server 120 isimplemented by a conventional server computer, such as a Windowsoperating system personal computer-based server, typically incommunication with one or more medical imaging modalities or imagestorage systems so as to provide a source of medical images. In someembodiments, server 120 includes a cache 121 in which select versions ofimages are stored. In one embodiment, cache 121 stores images that havenot yet been read, with the expectation that a request will beforthcoming for such images. In another embodiment, cache 121 storescompressed versions of images that may have been created by variousother processing in the environment in which system 100 operates.Network 110 is, in one embodiment, a conventional data network, forinstance an existing local area network or wide area network. In actualinstallations, it is typical for a health care organization to have anumber of viewing workstations 101 and a number of servers 120,interconnected by a variety of networks 110. For example, a radiologyclinic may have a viewing workstation connected to an image repositorythrough a dedicated high speed local area network, while a specialtyradiologist may from time to time be asked to review images accessibleonly over a relatively slow and fragile Internet connection from someremote facility.

Furthermore, even a single existing network 110 may have characteristicsthat change over time. During periods of light usage, the availablebandwidth that network 110 provides to a user of viewing workstation 101may be very large, while at peak times with many users sharing network110, the available bandwidth may be significantly reduced. In additionto bandwidth, in some embodiments other parameters related to imagetransfer are evaluated in addition to or instead of bandwidth. In somefacilities, different types of images may be stored, each of which hasdifferent preferred mechanisms for transfer. If a lossy compressedultrasound cineloop image is what is stored in server 120, differentmechanisms for transfer may be sought than if the image is a highresolution, uncompressed DICOM image. Likewise, it may not beappropriate to use wavelet-based processing as detailed below for imagesthat are stored in JPEG format. For purposes of illustration, thediscussion herein will focus on bandwidth as the parameter of interest.

In one embodiment, viewing workstation 101 includes an image viewersubsystem that processes image data received from network 110 andtransforms it into a form that can be displayed on viewing workstation101 for medical diagnosis or any other desired use. Viewing workstation101 further includes a bandwidth measurement subsystem 102 thatdetermines the expected available bandwidth for image transfer toworkstation 101.

Bandwidth measurement subsystem 102 initiates a transfer from server 120by requesting from the server a small data stream of fixed size. Bymeasuring the amount of time that it takes to transmit the data stream,the bandwidth measurement subsystem 102 estimates the likely bandwidththat will be available for the image transfer. To ensure that the datastream used for measurement is fetched from the server and not somecache of an intermediate proxy server, in one embodiment the subsystem102 requests slightly different and not readily predictable URLs (webaddresses) each time it tests for bandwidth. This is to minimize thelikelihood that the information will really be retrieved from server120, rather than some intermediate cache as may exist somewhere onnetwork 110 between server 120 and viewing workstation 101. In oneembodiment, some amount of pseudo-randomness is included in the lowestlevel of the URL to achieve this result. Furthermore, in one embodimentURLs are selected to minimize the likelihood that the content at thatURL will be amenable to significant automatic compression whentransmitted from server 120 to network 110. Some networks in whichsystem 100 are used include such automatic compression that, if highlycompressible test data were used, would falsely indicate a bandwidththat could not be achieved with real data. In one embodiment, thebandwidth measurement is performed at fixed time intervals, for eachserver the client is connected to at that given time. In an alternateembodiment, bandwidth measurement subsystem uses historical data fortransfers over each of several possible network paths to determineexpected bandwidth. In still another embodiment, image transfer iscommenced assuming a high, stable bandwidth and actual bandwidth isdetermined based on image streaming not meeting the expected rate. Instill another embodiment, bandwidth measurement is checked occasionallyduring streaming, so that the streaming mode changes dynamically inresponse to changes in usable network bandwidth.

As illustrated in FIG. 1, bandwidth measurement subsystem 102 isimplemented on viewing workstation 101. In an alternate embodiment,bandwidth measurement subsystem 102 is implemented on server 120 ratherthan viewing workstation 101. In still a third embodiment, bandwidthmeasurement subsystem is implemented separately from both viewingworkstation 101 and server 120.

Image viewer 103 is configured to process image data in severalmodes/formats, as further discussed below. Factors influencing theselection of available modes and formats include expected range ofnetwork bandwidths and reliability, expected available processing powerat both viewing workstation 101 and server 120, and medical practicerequirements for the images to be viewed on workstation 101. Forexample, in some applications, streaming data is computed “on the fly”by server 120, and in those cases processing limitations of server 120are factors in selection of a particular streaming mode.

Referring now to FIG. 2, a flow diagram of processing in accordance withone embodiment is shown. First, bandwidth measurement subsystem 102determines the available bandwidth for image transfer, as discussedabove. If the bandwidth is above a particular threshold (denoted forconvenience as “5” in FIG. 2), viewing workstation 101 requests server120 to transmit image information in native format, in this instance,the original DICOM file corresponding to the image, and that file istransmitted 203. In this circumstance, transfer of the entire image fileis made, regardless of whether the user of workstation 101 has aparticular region of interest (ROI) within the image.

If it is determined 205 that the bandwidth is not above the “5”threshold but is above another threshold (denoted as “4” in FIG. 2),workstation 101 requests server 120 to transmit 205 the entire data filein a lossless compression mode. In certain embodiments, compression viaconventional efficient, computationally non-intensive methods includinglossless JPEG, ZIP and the like are appropriate for this mode oftransmission.

Should the bandwidth be determined 206 to be below the “4” threshold butabove a “3” threshold, workstation 101 requests server 120 to transmit207 only the pixels needed for an ROI of the image. In this instance,some additional processing by the server is required, for instance tolow-pass filter the image data so as to provide a low-resolution view ofthe image that will allow selection of the ROI. In one embodiment, theROI is transmitted with no further processing of the pixels within thatROI; in another embodiment a fast compression scheme is applied to theROI pixels.

In the event that determination 208 reveals the bandwidth to be belowlevel “3” but above a level “2”, then workstation 101 requests server120 to transmit 209 the image file using baseline wavelet losslesscompression. In this mode of transmission, the server codes and streamsthe image using a moderate computationally demanding wavelet-basedalgorithm such that visual data can still be streamed in layers ofquality or resolution. Examples of such transmission are discussed inU.S. Pat. No. 6,314,452. In this mode, the emphasis is on the ability ofthe image viewer subsystem 103 to perform fast decoding and rendering ofthe streamed data. In one embodiment, at this level a waveletrepresentation of the ROI is encoded using simple variable length codingand transmitted by resolution, and computionally intensive codingcomponents such as arithmetic coding are not used, in order to reducethe overall processing overhead imposed by this transmission. Asmentioned above, such management of overhead is needed where server 120has significant processing limitations.

Should it be determined 208 that the bandwidth is below level 2, theneed for processing of the image data increases, and so more processingoverhead is accepted. In this instance, workstation 101 requests server120 to transmit 210 image information using progressive wavelet losslesscompression. In this mode the server encodes and streams the ROI in finelayers of visual quality, using computationally intensive methods. Thisensures a best possible rate-distortion performance, i.e., that thequality of the image rendered at the client is the best possible for thegiven amount of data transmitted, at each point in time during theinteraction.

In one embodiment, level “5” is a bandwidth of approximately 100 MB/s,level 4 is approximately 50 MB/s, level 3 is approximately 20 MB/s andlevel 2 is approximately 5 MB/s. In alternate embodiments differentnumbers of levels, and different thresholds are used. For example, alower bandwidth denoted as level 1 may be used, in which lossycompression is allowed and the user is warned that the streamed image islossy. Some medical applications may allow use of such lossycompression, but many will not.

In an alternate embodiment, some image information stored in server 120may already be in lossy form as well as in lossless form, in which casealternate modes (such as direct transmission of the entire lossy form)may be available for use. In some applications, other processing systemswill already have created different versions of image files, forinstance lossy compressed versions, for other purposes, and those may bestored in cache 121 for ready access as needed. Should processingoverhead on the server side be a concern, such use of cache 121 reducesthe need for repeated compression processing by server 120.

The selection of bandwidth thresholds and modes of transmission is notlimited to the example discussed above. For example, if workstation 101has only modest processing capability, modes of transmission thatrequire significant decoding by workstation 101 would be disfavored morethan if workstation 101 has robust processing capability.

Similarly, characteristics of the network 120 and of the imagesthemselves will call for particular choices of transmission modes, andthresholds. Should images be very large in comparison with networkbandwidth, it may be beneficial to switch to an ROI-based mode morequickly than otherwise.

The selection of mode is not limited to an a priori choice. In oneembodiment, a user may adaptively switch among available modes asdesired. In another embodiment, mode switching is automaticallyaccomplished when a change in network performance is detected and whenactual performance differs from what was originally expected.

The embodiment described above has control implemented on the clientside (i.e., at viewing workstation 101). In another embodiment, server120, or even an external device (not shown) could make bandwidthdeterminations and mode selections.

In the embodiment described herein, server 120 need only store theoriginal (e.g., DICOM) form of an image, without the need forpre-processing or duplication of data. On the other hand, if suchadditional versions of the image are already on the server as the resultof other processing, those versions are available to be used as well,and may be stored in cache 121.

Upon reading this disclosure, those of skill in the art will appreciatestill additional alternative structural and functional designs for asystem and process for transactional storage and workflow routing formedical image objects. Thus, while particular embodiments andapplications of the present invention have been illustrated anddescribed, it is to be understood that the invention is not limited tothe precise construction and components disclosed herein and thatvarious modifications, changes and variations which will be apparent tothose skilled in the art may be made in the arrangement, operation anddetails of the method and apparatus of the present invention disclosedherein without departing from the spirit and scope of the invention asdescribed in the appended claims.

1. An imaging system, comprising: a server that stores medical imageinformation and transmits the medical image information in a pluralityof transmission modes, wherein one transmission mode is a native fileformat, and each of a remaining transmission modes of the plurality oftransmission modes comprise a different compression technique; a networkadapted to transmit the medical image information from the server; aviewing workstation operatively coupled with the network, the viewingworkstation comprising a bandwidth measurement system that initiates atransfer of medical image information from the server to the viewingworkstation by estimating an available bandwidth for the transfer ofmedical image information from the server to the viewing workstation;wherein the viewing workstation receives the estimate of the availablebandwidth from the bandwidth measurement system and selects atransmission mode from the plurality of transmission modes, theplurality of transmission modes organized in a hierarchy of transmissionmodes, each of the transmission modes of the plurality being associatedwith a threshold bandwidth value, and the viewing workstation selectsthe transmission mode from the plurality of transmission modes bycomparing the estimate of the available bandwidth to a plurality ofthreshold bandwidth values; wherein the viewing workstation requeststransmission of the medical image information from the server and theviewing workstation requests the selected transmission mode for atransmission of the medical image information from the server; whereinif the selected transmission mode is one of the remaining transmissionmodes, the server compresses the medical image information in accordancewith the compression technique of the requested transmission mode, andtransmits the medical image information to the viewing workstation. 2.An imaging system as in claim 1, wherein the plurality of transmissionmodes includes transmission of original image files, transmission oflosslessly compressed image file data, transmission of region ofinterest pixel data, transmission of wavelet lossless compression imagefile data, and transmission of region of interest wavelet losslesscompression data.
 3. An imaging system as in claim 1, wherein theplurality of modes includes transmission of a lossy compressed versionof image data in response to the server having pre-existing access tothe lossy compressed version.
 4. An imaging system as in claim 1,wherein the viewing workstation is configured to request transmission insaid one of the plurality of modes responsive to performancecharacteristics of the viewing workstation relative to characteristicsof the medical image information.
 5. A method of transmitting medicalimage information within a picture archiving and communications system(PACS) including a server communicatively coupled to a viewingworkstation via a communications network, the method comprising: storingmedical image information at the server; initiating a transfer ofmedical image information from the server to the viewing workstationwith the viewing workstation; determining, an available bandwidth of thecommunications network, with a bandwidth measurement system, between theserver and the viewing workstation; establishing, with the viewingworkstation, a hierarchy of transmission modes wherein each of thetransmission modes in the hierarchy is associated with a thresholdbandwidth value; selecting, with the viewing workstation, a transmissionmode from a plurality of transmission modes wherein one transmissionmode of the plurality is a native file format and each of a remainingtransmission modes of the plurality comprise a different compressiontechnique, the selection of the transmission mode includes comparing thedetermined bandwidth of the communications network to a plurality ofthreshold bandwidth values; requesting, from the viewing workstation tothe server, the transfer of specified medical image information from theserver to the viewing workstation; requesting, from the viewingworkstation to the server, the selected transmission mode for thetransfer of the specified medical image information from the server tothe viewing workstation; and processing the medical image informationwith the server into the selected transmission mode; transmitting themedical image information in the selected transmission mode from theserver to the viewing workstation via the communications network.
 6. Amethod as in claim 5, further comprising: determining, with the server,a pre-processing capability of the server; determining, with the viewingworkstation, a post-processing capability of the viewing workstation;providing the pre-processing capability of the server to the viewingworkstation and wherein the viewing workstation determines the pluralityof threshold bandwidth values based upon the pre-processing andpost-processing capabilities each threshold bandwidth value of theplurality is associated with one of the plurality of transmission modes.7. A method as in claim 6, wherein selecting includes the viewingworkstation selecting a transmission mode associated with a highestthreshold value met by the bandwidth.
 8. The method of claim 5, whereineach of the transmission modes in the hierarchy is associated with athreshold bandwidth value, and the viewing workstation selects atransmission mode from the hierarchy that is associated with the highestthreshold bandwidth value achieved by the determined bandwidth of thecommunications network.
 9. The method of claim 7, further comprisingcontinuously determining the bandwidth of the network wherein a changein the determined bandwidth of the network results in the viewingworkstation selecting a different transmission mode of the plurality oftransmission modes.
 10. The method of claim 8, wherein the hierarchy oftransmission modes comprises, in descending order, based upon thethreshold bandwidth value: transmission of original image files,transmission of losslessly compressed image file data, transmission ofregion of interest pixel data, transmission of wavelet losslesscompression image data, transmission of region of interest waveletlossless compression image data, transmission of lossy compression imagedata, and transmission of compressed region of interest image data. 11.The method of claim 5, further comprising: requesting with the bandwidthmeasurement system a data stream of a fixed size from the server;transmitting the data stream from the server to the bandwidthmeasurement system; measuring a time with the bandwidth measurementsystem for the transmission of the data stream to the bandwidthmeasurement system; wherein the bandwidth of the network is estimatedbased upon the measured time.
 12. The method of claim 11, wherein thebandwidth measurement system requests the data stream of a fixed sizefrom a different URL each time the bandwidth of the network is estimatedfurther comprising a test URL with the bandwidth measurement system forthe data stream, wherein the test URL is fetched to minimize thetransmission of cached data.
 13. The method of claim 12, wherein eachpossible URL for the data stream request contains pseudo-randomness. 14.The method of claim 5, further comprising: determining with the viewingworkstation, an identification of an image type of the medical imageinformation; and wherein the selection of the transmission mode isfurther based upon the identification of the image type.
 15. The systemof claim 1, further comprising a plurality of servers that each storemedical image information, each of the plurality of servers arecommunicatively connected to the viewing workstation by the networkwherein the viewing workstation initiates a transfer of medical imageinformation from a one server of the plurality of servers to the viewingworkstation and the bandwidth measurement subsystem estimates anavailable bandwidth across the network between the one server and theviewing workstation, the viewing workstation requests the medical imageinformation and the selected transmission mode for the transmission ofmedical image information from the one server to the viewingworkstation.
 16. The system of claim 15, wherein the estimated availablebandwidth is between the viewing workstation and the one serverindependent from to an estimated bandwidth between the viewingworkstation and each of the other servers of the plurality.
 17. Themethod of claim 5, wherein the PACS includes a plurality of serverscommunicatively coupled to the viewing workstation via thecommunications network, and wherein determining the bandwidth of thecommunications network comprises determining the bandwidth of thecommunications network between the viewing workstation and a server ofthe plurality of servers and the viewing workstation requests thetransfer of specified medical image information and the selectedtransmission mode to the server of the plurality of servers for thetransmission of the specified medical image information from the serverof the plurality of servers to the viewing workstation.